1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive material, a piezoelectric/electrostrictive body, and a piezoelectric/electrostrictive element.
2. Description of the Related Art
Hitherto, piezoelectric/electrostrictive elements have been known to control a small displacement on the order of submicrons. In particular, in addition to their excellent controllability at a small displacement, piezoelectric/electrostrictive film elements have excellent characteristics, such as a high electromechanical conversion efficiency, high-speed responsivity, high durability, and lower power consumption. The piezoelectric/electrostrictive film elements include a piezoelectric/electrostrictive portion composed of a piezoelectric/electrostrictive ceramic composition (piezoelectric/electrostrictive material) and electrodes alternately stacked on a ceramic substrate. The piezoelectric/electrostrictive elements have found use in a variety of applications, such as piezoelectric pressure sensors, probe drive mechanisms in scanning tunneling microscopes, rectilinear guide mechanisms in ultraprecision machining apparatuses, hydraulic servo valves, videocassette recorder heads, pixels in flat-panel image display apparatuses, and ink-jet printer heads.
The piezoelectric/electrostrictive ceramic composition of a piezoelectric/electrostrictive portion has also been studied. For example, Japanese Examined Patent Application Publications No. 44-17103 and No. 45-8145 disclose a piezoelectric/electrostrictive ceramic composition of a Pb(Mg1/3Nb2/3)O3—PbZrO3—PbTiO3 (PZT) three-component solid solution or a piezoelectric/electrostrictive ceramic composition in which part of Pb atoms in the PZT are substituted by Si or La. The piezoelectric/electrostrictive characteristics of a piezoelectric/electrostrictive element primarily depend on a piezoelectric/electrostrictive portion. Thus, a piezoelectric/electrostrictive element that includes a piezoelectric/electrostrictive portion having excellent piezoelectric/electrostrictive characteristics (for example, piezoelectric distortion constant) is desired.
In recent years, environmental impacts such as leaching of lead (Pb) caused by acid rain have been becoming an important issue. In consideration of the environmental impacts, Japanese Unexamined Patent Application Publications Nos. 2001-261435, 2004-75449, 51-12700, and 11-171643, Japanese Patent No. 3830345, and Tadashi Takenaka et al., SILICATES INDUSTRIELS, 7-8, 136-142 (1993) describe lead-free piezoelectric/electrostrictive materials, such as a (Bi,Na)TiO3 piezoelectric/electrostrictive ceramic composition, which can provide a piezoelectric/electrostrictive body or a piezoelectric/electrostrictive element each having excellent piezoelectric/electrostrictive characteristics.
However, piezoelectric/electrostrictive bodies or piezoelectric/electrostrictive elements formed of the lead-free piezoelectric/electrostrictive ceramic compositions hardly achieve a larger displacement than piezoelectric/electrostrictive bodies formed of PZT compositions. Hence, the PZT compositions are presently superior to the lead-free compositions in piezoelectric/electrostrictive characteristics. Thus, there is a need to develop a lead-free piezoelectric/electrostrictive material that can provide a piezoelectric/electrostrictive body and a piezoelectric/electrostrictive element each having excellent piezoelectric/electrostrictive characteristics.